Method and system for authenticating an accessory

ABSTRACT

A method, system, and connector interface for authenticating an accessory. The method includes performing a first authentication operation on the accessory by the media player, where an authentication certificate is validated; and performing a second authentication operation on the accessory by the media player, where an authentication signature is validated. According to the system and method disclosed herein, the media player and accessory may utilize a plurality of commands utilized in a variety of environments such as within a connector interface system environment to control access to the media player.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation-In-Part of co-pending U.S. patent application Ser. No. 10/833,689, entitled “Connector Interface System for a Multi-Communication Device”, filed on Apr. 27, 2004, and assigned to the assignee of the present application.

FIELD OF THE INVENTION

The present invention relates generally to electrical devices and more particularly to electronic devices such as media players that communicate with accessory devices.

BACKGROUND OF THE INVENTION

A media player stores media assets, such as audio tracks or photos that can be played or displayed on the media player. One example of a media player is the iPod® media player, which is available from Apple Computer, Inc. of Cupertino, Calif. Often, a media player acquires its media assets from a host computer that serves to enable a user to manage media assets. As an example, the host computer can execute a media management application to manage media assets. One example of a media management application is iTunes®, version 6.0, produced by Apple Computer, Inc.

A media player typically includes one or more connectors or ports that can be used to interface to the media player. For example, the connector or port can enable the media player to couple to a host computer, be inserted into a docking system, or receive an accessory device. There are today many different types of accessory devices that can interconnect to the media player. For example, a remote control can be connected to the connector or port to allow the user to remotely control the media player. As another example, an automobile can include a connector and the media player can be inserted onto the connector such that an automobile media system can interact with the media player, thereby allowing the media content on the media player to be played within the automobile.

Numerous third-parties have developed accessories for use with media players. An accessory may be used with the media player as long as a compatible connector or port is utilized. Accessories interact with the media player using an accessory protocol. One example of an accessory protocol is referred to as iPod Accessory Protocol (iAP), which is available from Apple Computer, Inc. of Cupertino, Calif. The accessory protocol includes commands which have been typically been made freely accessible to accessory developers. A problem with the commands being freely accessible is that they can be used by unauthorized or counterfeit accessory devices.

One solution is to perform authentication operations on an accessory device. Accordingly, the accessory devices would not have any access to the media player until after the authentication process is complete.

Thus, there is a need for improved techniques to control the nature and extent to which accessory devices can be utilized with other electronic devices.

SUMMARY OF THE INVENTION

A method, system, and connector interface for authenticating an accessory are disclosed. The method includes performing a first authentication operation on the accessory by the media player, where an authentication certificate is validated; and performing a second authentication operation on the accessory by the media player, where an authentication signature is validated.

According to the system and method disclosed herein, the media player and accessory may utilize a plurality of commands utilized in a variety of environments such as within a connector interface system environment to control access to the media player.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B illustrate a docking connector in accordance with the present invention.

FIG. 2A is a front and top view of a remote connector in accordance with the present invention.

FIG. 2B illustrates a plug to be utilized in the remote connector.

FIG. 2C illustrates the plug inserted into the remote connector.

FIG. 3A illustrates the connector pin designations for the docking connector.

FIG. 3B illustrates the connection pin designations for the remote connector.

FIG. 4A illustrates a typical FireWire connector interface for the docking connector.

FIG. 4B illustrates a reference schematic diagram for an accessory power source.

FIG. 4C illustrates a reference schematic diagram for a system for detecting and identifying accessories for the docking connector.

FIG. 4D is a reference schematic of an electret microphone that may be connected to the remote connector.

FIG. 5A illustrates a media player coupled to different accessories.

FIG. 5B illustrates the media player coupled to a computer.

FIG. 5C illustrates the media player coupled to a car or home stereo system.

FIG. 5D illustrates the media player coupled to a dongle that communicates wirelessly with other accessories.

FIG. 5E illustrates the media player coupled to a speaker system.

FIG. 6 is a flow chart, which illustrates a process for controlling access to a media player.

FIG. 7 is a flow chart, which illustrates a process for authenticating an accessory.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates generally to electrical devices and more particularly to electrical devices such as media players that communicate with accessory devices. The following description is presented to enable one of ordinary skill in the art to make and use the invention and is provided in the context of a patent application and its requirements. Various modifications to the preferred embodiment and the generic principles and features described herein will be readily apparent to those skilled in the art. Thus, the present invention is not intended to be limited to the embodiment shown but is to be accorded the widest scope consistent with the principles and features described herein.

A method and system in accordance with the present invention for authenticating an accessory. The method includes performing a first (background) authentication operation on the accessory by the media player, wherein an authentication certificate is validated. In one embodiment, the authentication operations are handled in the background such that the media player is operative to process commands after authentication has begun but before the authentication has completed. This allows the media player and the accessory to interact immediately rather than waiting until after the authentication process has completed successfully. The method also includes performing a second authentication operation on the accessory by the media player, wherein an authentication signature is validated. In one embodiment, the media player verifies the authentication signature using a public key provided in the certificate. The media player and accessory may utilize the plurality of commands utilized in a variety of environments to facilitate controlling access to the media player. One such environment is within a connector interface system environment such as described in detail hereinbelow.

Although the authentication of an accessory is described hereinbelow, one of ordinary skill in the art recognizes that the procedures described below may be applied to the authentication of the media player and would be within the spirit and scope of the present invention.

Connector Interface System Overview

To describe the features of the connector interface system in accordance with the present invention in more detail, refer now to the following description in conjunction with the accompanying drawings.

Docking Connector

FIGS. 1A and 1B illustrate a docking connector 100 in accordance with the present invention. Referring first to FIG. 1A, the keying features 102 are of a custom length 104. In addition, a specific key arrangement is used where one set of keys is separated by one length at the bottom of the connector and another set of keys is separated by another length at the top of the connector. The use of this key arrangement prevents noncompliant connectors from being plugged in and causing potential damage to the device. The connector for power utilizes a Firewire specification for power. The connector includes a first make/last break contact to implement this scheme. FIG. 1B illustrates the first mate/last break contact 202 and also illustrates a ground pin and a power pin related to providing an appropriate first mate/last break contact. In this example, the ground pin 204 is longer than the power pin 206. Therefore, the ground pin 204 would contact its mating pin in the docking accessory before the power pin 206, minimizing internal electrical damage of the electronics of the device.

In addition, a connector interface system in accordance with the present invention uses universal serial bus (USB), universal asynchronous receiver-transmitter (UART), and Firewire interfaces as part of the same docking connector alignment, thereby making the design more compatible with different types of interfaces, as will be discussed in detail hereinafter. In so doing, more remote accessories can interface with the media player.

Remote Connector

The connection interface system also includes a remote connector which provides for the ability to output and input audio, provides I/O serial protocol, and provides an output video. FIG. 2A is a front and top view of a remote connector 200 in accordance with the present invention. As is seen, the remote connector 200 includes a top headphone receptacle 202, as well as a second receptacle 204 for remote devices. FIG. 2B illustrates a plug 300 to be utilized in the remote connector. The plug 300 allows the functions to be provided via the remote connector. FIG. 2C illustrates the plug 300 inserted into the remote connector 200. Heretofore, all of these features have not been implemented in a remote connector. Therefore, a standard headphone cable can be plugged in, but also special remote control cables, microphone cables, and video cables could be utilized with the remote connector.

To describe the features of the connector interface system in more detail, please find below a functional description of the docking connector, remote connector and a command set in accordance with the present invention.

Docking and Remote Connector Specifications

For an example of the connector pin designations for both the docking connector and for the remote connector for a media player such as an iPod device by Apple Computer, Inc., refer now to FIGS. 3A and 3B. FIG. 3A illustrates the connector pin designations for the docking connector. FIG. 3B illustrates the connection pin designations for the remote connector.

Docking Connector Specifications

FIG. 4A illustrates a typical Firewire connector interface for the docking connector. The following are some exemplary specifications: Firewire power (8V-30V DC IN, 10 W Max). In one embodiment, Firewire may be designed to the IEEE 1394 A Spec (400 Mb/s).

USB Interface

The media player provides two configurations, or modes, of USB device operation: mass storage and media player USB Interface (MPUI). The MPUI allows the media player to be controlled using a media player accessory protocol (MPAP) which will be described in detail later herein, using a USB Human Interface Device (HID) interface as a transport mechanism.

Accessory 3.3 V Power

FIG. 4B illustrates the accessory power source. The media player accessory power pin supplies voltages, for example, 3.0 V to 3.3V+/−5% (2.85 V to 3.465 V) over the 30-pin connector and remote connector (if present). A maximum current is shared between the 30-pin and Audio/Remote connectors.

By default, the media player supplies a particular current such as 5 mA. Proper software accessory detection is required to turn on high power (for example, up to 100 mA) during active device usage. When devices are inactive, they must consume less than a predetermined amount of power such as 5 mA current.

Accessory power is grounded through the Digital GND pins.

FIG. 4C illustrates a reference schematic diagram for a system for detecting and identifying accessories for the docking connector. The system comprises:

a) A resistor to ground allows the device to determine what has been plugged into docking connector. There is an internal pullup on Accessory Identify within the media player.

b) Two pins required (Accessory Identify & Accessory Detect)

FIG. 4D is a reference schematic of an electret microphone that may be connected to the remote connector.

Serial Protocol Communication:

a) Two pins used to communicate to and from device (Rx & Tx)

b) Input & Output (0V=Low, 3.3V=High)

As mentioned previously, media players connect to a variety of accessories. FIGS. 5A-5E illustrate a media player 500 coupled to different accessories. FIG. 5A illustrates a media player 500 coupled to a docking station 502. FIG. 5B illustrates the media player 500′ coupled to a computer 504. FIG. 5C illustrates the media player 500″ coupled to a car or home stereo system 506. FIG. 5D illustrates the media player 500′″ coupled to a dongle 508 that communicates wirelessly with other devices. FIG. 5E illustrates the media player 500″″ coupled to a speaker system 510. As is seen, what is meant by accessories includes but is not limited to docking stations, chargers, car stereos, microphones, home stereos, computers, speakers, and accessories which communicate wirelessly with other accessories.

As mentioned previously, this connector interface system could be utilized with a command set for authenticating an accessory. In one embodiment, the accessory may be a host computer or any other electronic device or system that may communicate with the media player. It should be understood by one of ordinary skill in the art that although the above-identified connector interface system could be utilized with the command set, a variety of other connectors or systems could be utilized and they would be within the spirit and scope of the present invention.

As described above, accessories interact with the media player using a media player accessory protocol. An example of such a media player accessory protocol is the iPod Accessory Protocol (iAP). The media player accessory protocol refers to the software component executing on the media player that communicates with accessories over a given transport layer. The application of the media player may be, for example, a media player application framework presents menus/screens to the user. Media player commands are be associated with the processing of voice, video, and other data between the media player and the accessory. For example, commands may be associated with read operations and write operations to transfer and store information between the media player and the accessory. Accordingly, in one embodiment, for each command related to the media player, there is a reciprocal command for the accessory. In one embodiment, commands may be grouped and associated with specific accessory functionality.

Command Functionality

Although a plurality of commands is described hereinbelow, one of ordinary skill in the art recognizes that many other commands could be utilized and their use would be within the spirit and scope of the present invention. Accordingly, the list of commands below is representative, but not exhaustive, of the types of commands that could be utilized to authenticate an accessory. Furthermore, it is also readily understood by one of ordinary skill in the art that a subset of these commands could be utilized by a media player or an accessory and that use would be within the spirit and scope of the present invention. A description of the functionality of some of these commands is described below.

Authentication of an Accessory

In previous authentication methods, the accessory transmits an identification message to the media player, where the identification message indicates that the accessory supports certain commands and supports authentication. The media player then transmits an acknowledgment message to the accessory. The media player then blocks access by the accessory until the entire authentication process completes. The media player may display a “Connecting . . . ” screen. The media player then confirms that the authentication version number that the accessory provides is the correct version number. If so, the media player transmits a challenge to be signed by the device. The media player then validates the authentication signature using a public key based on a device ID from the accessory. The following describes improvements over the previous authentication methods, in accordance with the present invention.

FIG. 6 is a flow chart, which illustrates a process for controlling access to a media player, in accordance with the present invention. As FIG. 6 illustrates, the process begins in step 602 where the media player performs a background authentication operation on the accessory, while the authentication certificate is validated. More specifically, during the background authentication operation, the accessory transmits authentication information to the media player, and the media player receives and then validates the certificate contained in the authentication information. In one embodiment, the authentication information may also include an authentication version number. Authentication certificates are described in more detail below. As described in more detail below, the media player does not wait until the entire authentication process completes but instead allows certain access before the authentication process completes. Next, in step 604, the media player performs a second authentication operation on the accessory, where an authentication signature is validated. More specifically, during the authentication operation, the accessory transmits an authentication signature to the media player, and the media player receives and then validates an authentication signature. In one embodiment, the media player verifies the authentication signature using a public key. More detailed embodiments of the background authentication and authentication operations are described below in FIG. 7.

Although the authentication of an accessory is described herein, one of ordinary skill in the art recognizes that the procedures described herein may be applied to the authentication of the media player and would be within the spirit and scope of the present invention. For example, the same or similar steps described in FIG. 6 above and/or in FIG. 7 below may be utilized by an accessory to authentication the media player.

Authentication Certificates

Standard authentication certificates function as containers for data such as the certificate creator (issuer, country, etc.), certificate type, valid certificate date ranges, and other metadata. Authentication certificates, also referred to as certificates or certs, are generated and signed by one or more certificate authorities (CAs) and have a unique serial number. In one embodiment, the certificate may be stored in an authentication coprocessor chip on the accessory. Authentication certificates in accordance with the present invention contain not only the metadata as in a standard authentication certificate but also device class information and a public key, which are described in more detail below.

As described in more detail below, the media player verifies certificates using a public key that is issued by the CA. The media player may also use the public key to verify a signed challenge. Certificates are used to transfer the public key and other accessory-specific information to the media player. Such accessory-specific information may contain, for example, device class information about the accessory. The device class determines what commands the accessory is permitted to use with respect to the media player. In one embodiment, the media player may add permissible commands to existing classes or add new device classes by means of a media player firmware update. New accessories may be supported by the media player when the CA issues new certificates to the accessory vendor.

In one embodiment, if a certificate is somehow compromised and cloned in counterfeit devices, the compromised serial number may be added to a certificate revocation list (or CRL) on the media player to prevent devices using the certificate from authenticating successfully. If the certificate parser of the media player does not recognize the cert's device class, the media player will reject the certificate. In one embodiment, a certificate to be used for device authentication may have a preset lifespan (e.g., in the range of 1-5 years, etc.), which may be set, for example, by a date. In one embodiment, certificate expiration could be accomplished by adding device serial numbers to the CRL after the expiration date has passed.

FIG. 7 is a flow chart, which illustrates a process for authenticating an accessory, in accordance with the present invention. As FIG. 7 illustrates, the process begins in step 702 where the media player and accessory exchange messages to determine whether the accessory supports certain commands and supports immediate authentication. More specifically, in one embodiment, the accessory transmits an identification message to the media player. The identification message includes a device identification (ID) and an indication that the accessory supports certain commands and supports authentication. In a preferred embodiment, support for immediate authentication is required. The media player then transmits an acknowledgment message to the accessory. In one embodiment, the media player notifies the application of the media player of the media player that the accessory is attempting to access the media player.

As described above, in one embodiment, the authentication operations are handled in the background to allow multiple cryptography options (e.g., RSA or SFEE) with/without hardware acceleration to be used. As a result, the media player is operative to process device commands after authentication has begun, before the authentication has completed, and through its successful completion. When device authentication fails (e.g., retry count and/or maximum time has been exhausted), the media player could lockout processing of incoming commands and prevent the device from interacting with media player. Media player applications will need to permit non-risky device use once authentication has started. Risky behavior is defined as anything that could permanently alter the media player behavior or download unsafe media. Examples of risky behavior to be avoided could be to download executable media, or firmware updates. If authentication fails at some later point, the application of the media player could cancel any device-related activities and possibly report an error screen to the user (e.g., “Device is not supported”).

Referring still to FIG. 7, in step 704, during the background authentication operation, the media player transmits an authentication information request to the accessory. In one embodiment, the media player starts a timeout timer. Next, in step 706, the accessory transmits the authentication information to the media player. In one embodiment, the authentication information includes an authentication major version, an authentication minor version, and a public certificate, where the certificate may be divided up into sections if it is large (e.g., greater than 500 bytes). If the certificate is divided up into sections, upon receipt of the authentication information, the media player reassembles the certificate. When the certificate is fully assembled, the certification is parsed for device class information. The media player then converts a class number from the device class information into an allowed command mask. This mask is used to validate that the commands identified by the device are allowed by the certification. In other words, the media player validates the certificate based at least in part on the device class information.

Next, in step 708, the media player validates the authentication information. The authentication information may be invalid for a number of reasons. For example, the authentication information may be invalid if the authentication version is not valid, if the public certificate has expired or is on the certificate revocation list (CRL). If any of the authentication information is invalid, the background authentication operation fails. A failure will restart the authentication process (if a retry count and timeout limits have not been exceeded). The background authentication operation passes if the authentication version is validated and if the certification class commands have been determined to match or exceed those requested by an identify command of the media player, and if a certification chain has been verified. In one embodiment, non-risky media player command application functions and command processing is enabled while authentication process continues. In one embodiment, the media player may transmit a message to the accessory indicating a version information status.

Next, in step 710, during a second authentication operation, the media player transmits an authentication signature request to the accessory. The authentication signature request includes a random nonce/challenge to be signed by the device. The specific nonce/challenge length may vary and will depend on the specific implementation. Next, in step 712, the accessory transmits an authentication signature (i.e., a message with a signed challenge/signature) to the media player. Next, in step 714, upon receipt of the authentication signature, the media player validates the authentication signature (i.e., the signed challenge). In one embodiment, the media player verifies the signed nonce/challenge using a public key based on a device ID from the accessory. In a preferred embodiment, the media player verifies the signed nonce/challenge using a public key from the certification provided by the accessory.

In one embodiment, an accessory authentication process (AAP) is based on a public key/private key system where accessories have a private key and the media player has the associated public key. The accessory authentication process is closely integrated with accessory protocol commands and an accessory authentication process.

Before completing the authentication process, the media player transmits an authentication status message to the accessory indicating signature status and authentication process completion. The authentication passes if the media player verifies the authentication signature. Otherwise, the authentication process fails. If authentication passes, the application of the media player unblocks to allow user access to the device.

If the authentication process fails, the device port of the media player will lock out the accessory. Also, upon a failure, the media player de-authorizes the accessory to prevent the accessory from utilizing the media player resources. In one embodiment, media player may also transmit an authentication status to the application of the media player. For example, if the authentication fails, the application of the media player may display a “Connection Failed” message.

In one embodiment, the authentication operations may utilize a retry count and maximum timeout. Accordingly, in one embodiment, the authentication can also fail if the retry counter or maximum timeout is exceeded. Locking out a port prevents an accessory from simulating a detach or re-identifying in order to reset the authentication retry/timeout counters. In one embodiment, incoming packets may be deleted if a device port authentication state is set to “lockout.” This will prevent any locked out device packets from being processed. In one embodiment, if the failure is due to an accessory identifying more commands than allowed by the certificate, the device lockout will not be activated at authentication failure and the accessory may be permitted to re-identify.

A method, system, and connector interface for authenticating an accessory has been disclosed. The method includes performing a first authentication operation on the accessory by the media player, where an authentication certificate is validated. The method also includes performing a second authentication operation on the accessory by the media player, where an authentication signature is validated. According to the system and method disclosed herein, the media player and accessory may utilize a plurality of commands utilized in a variety of environments such as within a connector interface system environment to control access to the media player.

Although the present invention has been described in accordance with the embodiments shown, one of ordinary skill in the art will readily recognize that there could be variations to the embodiments and those variations would be within the spirit and scope of the present invention. For example, the present invention can be implemented using hardware, software, a computer readable medium containing program instructions, or a combination thereof. Software written according to the present invention is to be either stored in some form of computer-readable medium such as memory or CD-ROM, or is to be transmitted over a network, and is to be executed by a processor. Consequently, a computer-readable medium is intended to include a computer readable signal, which may be, for example, transmitted over a network. Accordingly, many modifications may be made by one of ordinary skill in the art without departing from the spirit and scope of the appended claims. 

1. A method for authenticating a device, the method comprising: performing a first authentication operation on one of an accessory and a media player by one of the respective media player and accessory, wherein a certificate is validated; and performing a second authentication operation on one of the accessory and the media player by one of the respective media player and accessory, wherein an authentication signature is validated.
 2. The method of claim 1 further comprising allowing one of the accessory and the media player to have access to one of the respective media player and accessory before the first and second authentication operations are complete.
 3. The method of claim 1 wherein the certificate is validated based at least in part on device class information.
 4. The method of claim 1 wherein the authentication signature is validated using a public key provided in the certificate.
 5. The method of claim 1 wherein immediate authentication is required.
 6. The method of claim 1 further comprising locking out one of the accessory and media player for a random period if any of the first and second authentication operations fail.
 7. A protocol for authenticating an accessory, the protocol comprising: a first plurality of commands for performing, by at least one of the media player and an accessory, a first authentication operation, wherein authentication information is validated; and a second plurality of commands for performing, by at least one of the media player and the accessory, a second authentication operation, wherein an authentication signature is validated.
 8. The protocol of claim 7 further comprising commands for allowing the accessory to have access to the media player before the first and second authentication operations are complete.
 9. The protocol of claim 7 wherein the certificate is validated based at least in part on device class information.
 10. The protocol of claim 7 wherein the authentication signature is validated using a public key provided in the certificate.
 11. The protocol of claim 7 wherein immediate authentication is required.
 12. The protocol of claim 7 further comprising commands for locking out the accessory if any of the first and second authentication operations fail.
 13. A portable device comprising: a media player; an interface coupled to the media player; and a command set in communication with the interface, wherein the command set controls access to the media player, the command set comprising: a first plurality of commands for performing, by at least one of the media player and an accessory, a first authentication operation, wherein authentication information is validated; and a second plurality of commands for performing, by at least one of the media player and the accessory, a second authentication operation, wherein an authentication signature is validated.
 14. The portable device of claim 13 further comprising commands for allowing the accessory to have access to the media player before the first and second authentication operations are complete.
 15. The portable device of claim 13 wherein the certificate is validated based at least in part on device class information.
 16. The portable device of claim 13 wherein the authentication signature is validated using a public key provided in the certificate.
 17. The portable device of claim 13 wherein immediate authentication is required.
 18. The portable device of claim 13 further comprising commands for locking out the accessory if any of the first and second authentication operations fail.
 19. An accessory comprising: a device for transferring data; an interface coupled to the device; and a command set in communication with the interface, wherein the command set controls access to the media player, the command set comprising: a first plurality of commands for performing, by at least one of the media player and an accessory, a first authentication operation, wherein authentication information is validated; and a second plurality of commands for performing, by at least one of the media player and the accessory, a second authentication operation, wherein an authentication signature is validated.
 20. The accessory of claim 19 further comprising commands for allowing the accessory to have access to the media player before the first and second authentication operations are complete.
 21. The accessory of claim 19 wherein the certificate is validated based at least in part on device class information.
 22. The accessory of claim 19 wherein the authentication signature is validated using a public key provided in the certificate.
 23. The accessory of claim 19 wherein immediate authentication is required.
 24. The accessory of claim 19 further comprising commands for locking out the accessory if any of the first and second authentication operations fail.
 25. A computer-readable medium containing program instructions for authenticating an accessory, the program instructions which when executed by a computer system cause the computer system to execute a method comprising: performing a first authentication operation on the accessory by the media player, wherein a certificate is validated; and performing a second authentication operation on the accessory by the media player, wherein an authentication signature is validated.
 26. The computer-readable medium of claim 25 further comprising program instructions for allowing the accessory to have access to the media player before the first and second authentication operations are complete.
 27. The computer-readable medium of claim 25 wherein the certificate is validated based at least in part on device class information.
 28. The computer-readable medium of claim 25 wherein the authentication signature is validated using a public key provided in the certificate.
 29. The computer-readable medium of claim 25 wherein immediate authentication is required.
 30. The computer-readable medium of claim 25 further comprising program instructions for locking out the accessory for a random period if any of the first and second authentication operations fail.
 31. A method for authenticating a media player, the method comprising: performing a first authentication operation on the media player by the accessory, wherein a certificate is validated; and performing a second authentication operation on the media player by the accessory, wherein an authentication signature is validated.
 32. The method of claim 31 further comprising allowing the media player to have access to the accessory before the first and second authentication operations are complete.
 33. The method of claim 31 wherein the certificate is validated based at least in part on device class information.
 34. The method of claim 31 wherein the authentication signature is validated using a public key provided in the certificate.
 35. The method of claim 31 wherein immediate authentication is required.
 36. The method of claim 31 further comprising locking out the media player for a random period if any of the first and second authentication operations fail. 